1. Field of the Invention
This invention generally relates to light disinfection systems and methods and, more specifically to, room and area disinfection systems and methods utilizing pulsed light with modulated power flux and light systems with visible light compensation between pulses.
2. Description of the Related Art
The following descriptions and examples are not admitted to be prior art by virtue of their inclusion within this section.
Pulsed light sources are used in a variety of applications to generate recurrent pulses of ultraviolet (UV) light. Examples of applications include but are not limited to polymer curing, food sterilization, fluid and object disinfection, and room/area decontamination. Area/room disinfection, in particular, is increasingly becoming an application of interest as pulsed UV light as been shown to significantly reduce the number of pathogenic microorganisms in an area/room in a short period of time. In particular, pulsed UV light has been shown to deactivate and, in some cases, kill microorganisms on objects and surfaces in a room/area at distances within approximately 3 meters from a UV light source, depending on factors such as reflectivity and complexity of objects in the room. In addition, pulsed UV light has been shown to reduce the number of pathogenic microorganisms within a room/area to a level considered much less harmful to human health in less than approximately 5 minutes. Examples of area/room disinfection applications are those used in hospitals and those used in agricultural operations, such as for breeding and/or farming animals.
Many studies suggest germicidal efficacy for microorganism deactivation is chiefly due to the dose of ultraviolet electromagnetic radiation subtype C (UVC) light applied as well as efficacy in the ultraviolet electromagnetic radiation subtype B (UVB), or the dose of energy within the wavelengths of 200 and 320 nanometers. This efficacy is determined by measuring quantum yield or the number of germicidal actions taking place per incident photon arriving on a microorganism. Conventional uses of pulsed UV light for UV sanitation of foods generally rely on a high level of power per pulse to maximize UVC dose, specifically such that the UV light may penetrate into crevices or pores of a food's surface. UV curing and sintering processes also utilize a relatively high level of power per pulse to maximize UV dose. In other applications which utilize pulsed UV light to deactivate microorganisms, such as wastewater disinfection, a relatively low pulse power may be used but at a relatively high frequency in order to maximize UVC dose for a given period of time. In particular, it is known that pulse power and pulse frequency each have an effect on UVC dose (however not necessarily a proportional effect), but have an inverse relationship relative to each other (i.e., the higher the power per pulse, the lower the pulse frequency and vice versa) and, thus, each can be varied depending on the needs of the application.
Area/room disinfection applications utilizing pulse UV light, however, induce limitations to which pulse power and pulse frequency may be optimized. In particular, area/room disinfection processes differ from other pulsed UV light processes (e.g., curing, sintering, food sanitization and wastewater treatment processes) in that the UV light must be transmitted a relatively long distance (e.g., up to 3 meters from a UV source). Due to the inverse-square law, conventional area/room disinfection applications utilizing pulsed UV light are generally limited to using a relatively high level of power per pulse to insure a sufficient dose of UVC is transmitted across a room/area. In order to maximize the UVC dose generated, conventional area/room disinfection applications utilizing pulse UV light use a relatively low pulse frequency (e.g., less than approximately 2 Hz). Despite the compromise of a relatively low pulse frequency, an area/room disinfection device utilizing pulse UV light may be limited in the power level it can generate for a pulse due to size limitations of the device. In particular, it is often preferred for area/room disinfection devices to be readily portable such that they may be moved to multiple rooms of a building and, thus, the size of the pulsed lamp and the power supply used to operate it may be limited. Other applications of pulsed UV applications (e.g., curing, sintering, food sanitization and wastewater treatment processes) are generally not designed for portability and, thus, are often not limited to the amount of UV light it can generate.
Furthermore, conventional area/room disinfection applications utilizing pulse UV light are generally limited to frequencies less than 2 Hz to the keep the pulse frequency from potentially inducing seizures (the range of which is generally considered to be 3-60 Hz). In particular, although area/room disinfection utilizing pulsed UV light is typically performed by an automated device in a vacated room/area to limit or prevent exposure of UV light, some rooms/areas may not block the visible light generated from the disinfection device. In order to limit exposure of the intensity and/or pulse rate of pulsed light, provisions are often used to shield transmission of visible light from the room/area, such as blocking windows of a room or shielding gaps at the top and/or bottom of a room divider. Such shielding provisions, however, may not block all light from all areas/rooms and, thus, the pulse frequency of an area/room disinfection device utilizing pulsed UV light may generally be less limited to 2 Hz or less for safety considerations.
In view of the general knowledge of germicidal efficacy of pulsed UV light being chiefly dependent on overall UVC dose and the aforementioned restrictions of area/room disinfection devices which use pulse UV light, the efficiency and efficacy of conventional area/room disinfection devices utilizing pulse UV light have been limited. Accordingly, it would be beneficial to develop methods and systems for increasing the efficiency and efficacy of area/room disinfection devices utilizing pulse UV light.